Problem connections cyrus

[Sera]

Sorry for my poor English:

I have problems with cyrus.
it's block 10-20 times a day, all days.
Don't crash, but suddenly don't accept any connections and the mua
display the message " the server reject the connection", or "max number
of connections reached".

I'm used two hosts:
1- debian sarge with cyrus and postfix
2- debian etch with postfix

The version of cyrus is 2.1.18-1+sarge2

My cyrus.conf is it:

# Debian defaults for Cyrus IMAP server/cluster implementation
# see cyrus.conf(5) for more information
#
# All the tcp services are tcpd-wrapped. see hosts_access(5)
# $Id: cyrus.conf,v 1.16 2003/11/05 01:04:22 hmh Exp $

START {
        # do not delete this entry!
        recover         cmd="/usr/sbin/ctl_cyrusdb -r"

        # this is only necessary if using idled for IMAP IDLE
        # this is NOT to be enabled right now in Debian builds
        #idled          cmd="idled"

        # this is useful on backend nodes of a Murder cluster
        # it causes the backend to syncronize its mailbox list with
        # the mupdate master upon startup
        #mupdatepush   cmd="/usr/sbin/ctl_mboxlist -m"

        # this is recommended if using duplicate delivery suppression
        delprune        cmd="/usr/sbin/ctl_deliver -E 3"
        # this is recommended if caching TLS sessions
        tlsprune        cmd="/usr/sbin/tls_prune"
}

# UNIX sockets start with a slash and are absolute paths
# you can use a maxchild=# to limit the maximum number of forks of a service
# you can use babysit=true and maxforkrate=# to keep tight tabs on the
service
# most services also accept -U (limit number of reuses) and -T (timeout)
SERVICES {
        # --- Normal cyrus spool, or Murder backends ---
        # add or remove based on preferences
        imap            cmd="imapd -U 30" listen="imap" prefork=0
maxchild=100
        imaps           cmd="imapd -s -U 30" listen="imaps" prefork=0
maxchild=100
        #pop3           cmd="pop3d -U 30" listen="pop3" prefork=0
maxchild=50
        #pop3s          cmd="pop3d -s -U 30" listen="pop3s" prefork=0
maxchild=50

        # At least one form of LMTP is required for delivery
        # (you must keep the Unix socket name in sync with imap.conf)
        lmtp            cmd="lmtpd" listen="11.0.0.12:lmtp" prefork=0
maxchild=20
        lmtpunix        cmd="lmtpd" listen="/var/run/cyrus/socket/lmtp"
prefork=0 maxchild=20
        # ----------------------------------------------

        # useful if you need to give users remote access to sieve
        # by default, we limit this to localhost in Debian
        sieve           cmd="timsieved" listen="localhost:sieve"
prefork=0 maxchild=100

        # this one is needed for the notification services
        notify          cmd="notifyd"
listen="/var/run/cyrus/socket/notify" proto="udp" prefork=1

        # --- Murder frontends -------------------------
        # enable these and disable the matching services above,
        # except for sieve (which deals automatically with Murder)

        # mupdate database service - must prefork at least 1
        # (mupdate slaves)
        #mupdate       cmd="mupdate" listen=3905 prefork=1
        # (mupdate master, only one in the entire cluster)
        #mupdate       cmd="mupdate -m" listen=3905 prefork=1

        # proxies that will connect to the backends
        #imap           cmd="proxyd" listen="imap" prefork=0 maxchild=100
        #imaps          cmd="proxyd -s" listen="imaps" prefork=0
maxchild=100
        #pop3           cmd="pop3proxyd" listen="pop3" prefork=0 maxchild=50
        #pop3s          cmd="pop3proxyd -s" listen="pop3s" prefork=0
maxchild=50
        #lmtp           cmd="lmtpproxyd" listen="lmtp" prefork=1 maxchild=20
        # ----------------------------------------------
}

EVENTS {
        # this is required
        checkpoint      cmd="/usr/sbin/ctl_cyrusdb -c" period=30

        # this is only necessary if using duplicate delivery suppression
        delprune        cmd="/usr/sbin/ctl_deliver -E 3" at=0401

        # this is only necessary if caching TLS sessions
        tlsprune        cmd="/usr/sbin/tls_prune" at=0401

        # para evitar squat failed en log
        squatter        cmd="/usr/sbin/squatter -r *" period=240
        #squatter_1      cmd="/usr/bin/nice -n 19 /usr/sbin/squatter -s
-r user" period=240
}




Any idea?
Thanks